Maximum Residue Research Articles

The effects of dietary dieldrin on residues in eggs and tissues of laying hens and the effects of phenobarbital and charcoal on these residues.

Laying hens were fed a total of 18 mg of dieldrin over an 11-day period. Some of these were fed charcoal and others received phenobarbital during the 11-day period. Neither treatment affected the amount of dieldrin residue in the eggs. The maximum dieldrin residue in the eggs was about 4 ppm and occurred about 20 days after the initial dosage or about 9 days after cessation of dosage. The dieldrin residue levels in the livers ranged from 0 to 228 ppb and the brains contained no dieldrin residue. No change in shell thickness of the eggs or weights of the chickens was noted.

Aquatic Midge Larvicides, Their Efficacy and Residues in Water, Soil, and Fish in a Warm-Water Lake1

To study the efficacy of chemical larvicides; several materials were evaluated in two warm-water southern California artificial lakes, (Lake Calabasas and Westlake) and the residues of an effective larvicide (chlorpyrifos) in various components of one of the lakes were investigated. Abate® ( O,O' -(thiodi- p -phenylene) O,O,O',O' -tetramethyl phosphorothioate) gave excellent control of Chironomine midges ( Chironomus and Dicrotendipes spp.) but only mediocre or poor control of the smaller Tanypodine midges ( Cricotopus and Tanypus spp.). Carbaryl yielded poor control of both groups, and fenitrothion yielded good control of both groups at a higher rate of application. Chlorpyrifos gave excellent control of both groups of midges. It was more effective against the Chironomine larvae. This material at 0.2 lb active ingredients per acresurface yielded complete control of Chironomine midges for 12 weeks or longer, but suppressed the Tanypodine larvae for only 7–8 weeks. Residues of chlorpyrifos (used as 2% granules) were generally higher in the bottom water, even though maximum residues in both layers reached 0.6 ppb. Residues were much higher in the mud, reaching a mean maximum of 0.3 parts per million in the top 1-inch section of mud samples, but only traces were found in the remaining section of the mud. Maximum residues in water were obtained one day after treatment, declining to below 0.1 ppb within 4 weeks after treatment. The maximum residues in the mud were obtained one week after treatment, declining to below 0.1 ppm in 28 days. Slightly higher levels of residues were found in water and mud when the whole lake was treated. Bottom-dwelling and -frequenting fish, such as channel catfish ( Ictalurus punctatus Rafinesque) and, to some extent, black crappie ( Pomoxis nigromaculatus LeSueur), contained much higher quantities of chlorpyrifos than the nonbottom dwelling fish such as largemouth bass ( Micropterus salmoides Lacepede) and bluegill ( Lepomis microchirus Rafinesque). Mean maximum residues in channel catfish and black crappie were 0.8 and 0.5 ppm after 3 and 2 weeks posttreatment, respectively, declining to barely detectable levels 25 days after treatment. The residues in largemouth bass and bluegill were minimal, with maximum approaching 0.2 ppm but remaining 0.1 or below this level most of the time.

Malathion on milling fractions of three varieties of rough rice: duration of protection and residue degradation.

Malathion deposits of about 11, 17, and 20 ppm protected rough rice for 6 to 12 months under Gulf Coast environmental conditions. Protection lasted slightly longer in bin tests than in jar tests. Residues on rough rice greater than 8, 4, and 2 ppm were required to control confused flour beetles, Tribolium confusum Jacquelin duVal; lesser grain borers, Rhyzopertha dominica (F.); and rice weevils, Sitophilus oryzae (L.), respectively. Initial deposits on rough rice were 20 ppm; deposits decreased to levels below 8 ppm within 3 months. Initial deposits on hulls were 80 ppm; deposits did not fall below 8 ppm for 7 to 11 months. Residues on bran and milled rice increased for 3 months and then declined. Residues on bran reached a maximum of 30 ppm but fell below 8 ppm in 6 to 10 months; on milled rice. maximum residue was 0.32 ppm. Varieties of bran and milled rice retained malathion in the following order: ‘Belle Patna’ > ‘Nato’ > ‘Dawn.’ This ranking apparently was dependent upon the relative surface area and the thickness of the covering hull on kernels of each variety.

Absorption and translocation of diazinon by rice plants from submerged soils and paddy water and the persistence of residues in plant tissues.

Diazinon applied to paddy water was readily absorbed by rice roots and translocated to the leaf sheath and leaf blade. Maximum residues in plant tissues were recovered 5 days after application but declined rapidly thereafter. This insecticide loss observed in plant tissues between 5 and 10 days was greater following a 2nd application. Diazinon persisted longer in the standing water of covered unplanted pots than in water of uncovered unplanted pots, indicating that the insecticide volatilized in the latter. Greater loss of the insecticide from the standing water and soils following the 2nd application appeared to be due to increased absorption by the older plants and to the establishment of a diazinon-degrading microbial factor in the paddy water in response to the first application. Paddy water collected from plots that had received several diazinon applications caused faster degradation of diazinon than the water from untreated plots. This diazinon degradation property was minimized but not eliminated even after the plots were drained and reirrigated.

The Metabolism of P32-Labeled Ciodrin in a Lactating Goat

A study was made of the metabolism of P32-labeled Ciodrin®, alpha -methylbenzyl 3-bydroxycrotonate dimethl phosphate, by a dermally treated milk goat. Eleven percent of the applied dose was eliminated in the urine. Only minute quantities of radioactive material appeared in the feces and milk. Dimethl phosphoric acid accounted for 79.7 to 91.2% of the radioactive material in the urine. No radioactive material could be extracted from the blood, and the maximum true residue in the milk was only 0.20 ppb.